Semiconductor integrated circuit device with enhanced resistance to electrostatic breakdown

ABSTRACT

A semiconductor integrated circuit device having a plurality of internal circuits connected to different power lines, and an inter-circuit signal wire or a branched wire along these internal circuits, wherein near an active element in a first connection configuration connected to the inter-circuit signal wire or the like, a plurality of active elements in a second connection configuration are arranged to sandwich or surround the active element in the first connection configuration. The active elements in the second connection configuration have the identical or similar structure to the active element in the first connection configuration, and are connected to power lines of an internal circuit associated therewith but not connected to signal wires and so on in the internal circuit.

This is a Divisional of copending U.S. application Ser. No. 09/625,643,filed on Jul. 25, 2000.

This application claims the benefit of Japanese application No.11-213098, filed Jul. 28, 1999, and Japanese application No. 11-213123,filed Jul. 28, 1999, which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor integratedcircuit devices having a plurality of internal circuits having differentsupply voltages, and more particularly to the technology for protectingactive elements in such internal circuits from failure due toelectrostatic discharge or the like.

The semiconductor integrated circuit devices directed by the presentinvention may include a multi-functional LSI (large scaled integratedcircuit device), a digital/analog hybrid LSI, a digital LSI formulti-power supply, to name a few.

2. Description of Technical Background

FIGS. 10A and 10B illustrate a typical layout of a semiconductorintegrated circuit device, fabricated on a single chip, which has aplurality of internal circuits using different power lines, wherein FIG.10A is a schematic diagram generally illustrating the layout of thechip, and FIG. 10B is a circuit diagram of a main portion. FIGS. 11A to11E illustrate at an element level portions of the internal circuitswhich communicate signals therebetween, wherein FIG. 11A is a detailedcircuit diagram; FIG. 11B is a layout diagram of semiconductor regions;FIG. 11C is a layout diagram of the semiconductor regions in which gatesand power lines have also been patterned; FIG. 11D is a layout diagramof the semiconductor regions in which signal wires have further beenpatterned; and FIG. 11E is a vertically sectioned perspective viewillustrating a semiconductor region and a gate which constitute a basiccell or a basic unit for an active element. It should be noted that inFIG. 11D, thick solid lines indicate signal wires; black circlesindicate connections such as contact holes at which signal wires extenddeep into a semiconductor layer; and small squares indicate connectionsat which signal wires extend into a power line layer but not to theunderlying semiconductor layer. The same legends are applied to FIGS.1B, 2B, 4B, 5B and 8A, later described.

The generalization of manufacturing processes, automated designs and soon have been developed for large scaled integrated circuits, which areapplied in a wide variety of products, for example, gate arrays, customLSIs, ASICs (Application Specific IC), and so on, on the assumption ofthe common utilization of basic cell structures, regular layouts and soon. In many cases, external connection terminals, external signalinput/output circuits, and internal circuits are arranged in order fromthe periphery to the center of a semiconductor integrated circuitdevice. As described herein as a typical example, a semiconductorintegrated circuit device 1 (see FIG. 10A) includes an internal circuit4A and an internal circuit 4B which are supplied with different supplyvoltages, so that these internal circuits 4A, 4B are positionedseparately in a left-hand and a right-hand block. Also, a left-handexternal signal input/output circuit 3A and some external connectionterminals 2 on the left side, located near the left-hand internalcircuit 4A, are generally connected to the internal circuit 4A, and areadapted to relay signals associated with the internal circuit 4A to theoutside and to supply power to the internal circuit 4A. Remainingexternal signal input/output circuit 3B and external connectionterminals 2, in turn, are generally connected to the internal circuit4B, and are adapted to relay signals associated with the internalcircuit 4B to the outside and to supply power to the internal circuit4B.

A variety of combinations of supply voltages fed to these internalcircuits 4A, 4B may be contemplated, for example, 12 volts and 5 volts;5 volts and 3 volts; 3 volts and 2 volts, and so on. In the drawings,circuits fed with a relatively higher supply voltage (left-hand ones inFIG. 10A), elements contained therein, and so on are designated byreference numerals followed by “A,” while circuits fed with a relativelylower supply voltage (right-hand ones in FIG. 10B), elements containedtherein, and so on are designated by reference numerals followed by “B.”The same rule is applied also to FIGS. 12A to 12C and FIGS. 1A to 9,later described.

In such combinations, powering of the internal circuit 4A from theoutside requires at least one pair of power lines, for example, a powerline 8A for applying a positive voltage and a power line 9A forgrounding, so that at least one of multiple external connectionterminals 2 is assigned as a high power terminal 5A which is connectedto the one power line 8A, and at least one of the remaining externalconnection terminals 2 is assigned as a ground terminal 6A which isconnected to the other power line 9A. The power lines 8A, 9Aindividually extend as circular, tree-like, or stripe wires (see FIG.10A), not shown, and are connected to an input protection circuit 3AA inthe external signal input/output circuit 3A, and are further routedtherethrough to the internal circuit 4A in which they are also connectedto multiple internal elements 11A, 12A, 13A (see FIG. 10B) The inputprotection circuit 3AA (see FIG. 10B) is provided for a connection linewhich connects an input/output terminal 7A assigned to an input to theinternal element 11A or the like of the external connection terminals 2to a connection line with the internal element 11A. Typically, the inputprotection circuit 3AA may be composed of a pair or a set of rectifyingelements such as diodes, transistors or the like, connected to theconnection line and to the power lines 8A, 9A. If surge noise (ESDsurge: Electrostatic Discharge) such as static electricity introducesinto the input/output terminal 7A, the input protection circuit 3AAforces the surge noise to escape to the high power terminal 5A or theground terminal 6A to protect the internal element 11A from the surgenoise.

Likewise, in the internal circuit 4B (see FIGS. 10A, 10B), althoughrepetitive details are omitted, a power line 8B for applying a positivevoltage lower than that of the power line 8A is routed from a lowerpower terminal 5B through an external signal input/output circuit 3B tothe internal circuit 4B, while a power line 9B for grounding, forming apair with the power line 8B, is likewise routed from a ground terminal6B through the external signal input/output circuit 3B to the internalcircuit 4B. These lines are connected to an input protection circuit 3BBin the external signal input/output circuit 3B, as well as to internalelements 11B, 12B, 13B in the internal circuit 4B, and a connection linefrom the input/output terminal 7B to the internal element 11B isconnected to the input protection circuit 3BB. All of these power linesor at least the power lines 8A, 8B may be indirectly connected throughthe protection circuit or the like but will never be directly connectedor short-circuited within the semiconductor integrated circuit device 1,so that the internal circuit 4A, 4B act as a plurality of individualinternal circuits using different power lines.

Further, as can be seen in FIG. 10B, for communicating signals betweenthe internal circuits 4A, 4B, inter-circuit signal wires 12 forinterconnecting the output element 12A of the internal circuit 4A andthe input element 12B of the internal circuit 4B, and inter-circuitsignal wires 13 for interconnecting the output element 13B of theinternal circuit 4B and the input element 13A of the internal circuit 4Aare also routed between the internal circuits 4A, 4B as many number oflines as required for communicating signals.

The output element 12A may comprise a single or a plurality of activeelements such as transistors. For example, if the output element 12A isa CMOS invertor (see FIG. 11A), the output element 12A includes a p-typeMOS (hereinafter called the “pMOS”) transistor 12AP having a sourceconnected to the power line 8A, a drain connected to the inter-circuitsignal wire 12, and a gate connected to an internal signal wire SAwithin the internal circuit 4A; and an n-type MOS (hereinafter calledthe “nMOS”) transistor 12AN having a source connected to the power line9A, a drain connected to the inter-circuit signal wire 12, and a gateconnected to the internal signal wire SA within the internal circuit 4A.The input element 12B also includes a pair of transistors, pMOStransistor 12BP and nMOS transistor 12BN, having their sources connectedto the power lines 8B, 9B, respectively, which have their gatesconnected to the inter-circuit signal wire 12, and their drainsconnected to an internal signal wire SB within the internal circuit 4B.

The input element 13A and the output element 13B, though signals arecommunicated in directions opposite to each other, each includes asimilar transistor pair consisting of one pMOS transistor (13AP, 13BP)and one nMOS transistor (13AN, 13BN), with their drains or gatesconnected to the inter-circuit signal wire 13.

Each of the transistors 12AP, 12AN, 12BP, 12BN (and the transistors13AP, 13AN, 13BP, 13BN) is an active element connected to theinter-circuit signal wires in a first connection configuration.

Then, for fabricating the semiconductor integrated circuit device 1having the circuits as mentioned above on a silicon wafer or the like(see FIGS. 11B to 11E), miniature basic cells for active elements arerepeatedly arranged at regular pitches in the vertical and horizontaldirections in regions allocated to the internal circuits 4A, 4B in eachchip. For example, a basic cell for a CMOS (see FIG. 11B) is composed ofan nMOS cell and a pMOS cell. The nMOS cells are distributed on a p-typesubstrate (p-Sub) in the form of island, and an n-type semiconductorregion, a gate oxide film region, and an n-type semiconductor region maybe formed for each of the cells. Alternatively, n-type semiconductorregions, gate oxide film regions, n-type semiconductor regions, gateoxide film regions and n-type semiconductor regions may often bepreviously formed as illustrated, and a central n-type semiconductorregion is shared to fabricate two n-type MOS transistors.

The pMOS cells, in turn, are distributed likewise in the form of islandin a n-type well region (n-Well) and positioned to establish aone-to-one correspondence to the nMOS cells, and are implemented byreplacing the n-type semiconductor region in the nMOS cells with ap-type semiconductor region. Then, on a gate oxide film region of eachbasic cell, an isolated pattern made of a metal or the like isindividually formed to provide a gate and its lead-out (see FIG. 11E).Further, another conductive layer made of a metal, overlying a suitableinsulating layer or the like interposed therebetween, is patterned toform the power line 8A on a sequence of pMOS basic cells in the internalcircuit 4A; the power line 9A on a sequence of nMOS basic cells in theinternal circuit 4A; the power line 8B on a sequence of pMOS basic cellsin the internal circuit 4B; and the power line 9B on a sequence of MOSbasic cells in the internal circuit 4B (see FIG. 1C).

In this way, the basic cells for active elements are regularly arrangedin the same structure or similar structure until the midway ofpre-processing of the semiconductor process to provide highlygeneralized wafers.

Subsequently, as a specific allocation of active elements is determinedbased on a particular application, for example, the active elements12AP, 12AN in the first connection configuration are allocated toadjacent basic cells in the internal circuit 4A (see FIG. 11C), whilethe active elements 12BP, 12BN in the first connection configuration arelikewise allocated to adjacent basic cells in the internal circuit 4B.Consequently, necessary wires associated with these active elements aresubstantially uniquely determined in the following manner.

Specifically, as can be seen in FIG. 11D, basic cells of interest areformed with contact holes (see a black line in FIG. 11D) such as viaholes at the centers thereof to connect the sources of the activeelements 12AP, 12AN, 12BP, 12BN in the first connection configuration tothe power lines 8A, 9A, 8B, 9B, respectively. In the internal circuit4A, the internal signal wire SA is connected to the gate of the activeelement 12AP in the first connection configuration as well as to thegates of both the active elements 12AP, 12AN in the first connectionconfiguration. Also, one end of the inter-circuit signal wire 12 isbranched and connected to the drains of the active elements 12AP, 12ANin the first configuration at corners of the basic cells.

The other end of the inter-circuit signal wire 12 extends into theinternal circuit 4B and is connected to the gate of the active element12BP in the first connection configuration. In the internal circuit 4B,the active elements 12BP, 12BN in the first connection configurationhave their gates connected to each other. The internal signal wire SBhas its one end branched and connected to the drains of the activeelements 12BP, 12BN in the first connection configuration at corners ofthe basic cells. The branched signal wires are again joined andconnected to another internal element or the like in the internalcircuit 4B.

In this way, the basic semiconductor parts are generalized and utilizedin common, and a variety of circuits are implemented by changing theallocation of active elements, determined subsequent to the formation ofthe basic semiconductor parts, and the wiring formed on an overlyinglayer and so on, thereby making it possible to rapidly and preciselyrespond to a variety of applications.

3. Prior Art

Conventionally, the semiconductor integrated circuit device 1 asdescribed above is provided with an inter-block protection circuitbetween both the internal circuits 4A, 4B in addition to theaforementioned input protection circuits 3AA, 3BB, as countermeasures tothe electrostatic breakdown. Such an inter-block protection circuit iscomposed of resistors, rectifying elements, zener diodes or transistorshaving a similar function, and so on, and is also connected to the powerlines 8A, 8B, 9A, 9B on which different supply voltages are fed.

As increasing miniaturization of internal circuits results in lowerresistance of internal elements to electrostatic breakdown, theprotection against the electrostatic breakdown has been enhanced byenlarging the input protection circuits which are smaller in number thaninternal elements, and by increasing the number of inter-blockprotection circuits or enlarging the inter-block protection circuit.

SUMMARY OF THE INVENTION

Presentation of Problems

However, the trend of miniaturization and higher speed of internalcircuits is still growing without ceasing, so that repetitions of theconventional approach of increasing the protection circuits no longerprovide sufficient protection.

This is because the miniaturization of elements results in a lowerresistance of the elements themselves, such as a lower gate breakdown,and moreover reduces the ability of propagating, diffusing andmitigating surge noise because the capacitance associated with orparasitic to elements, wires and so on decreases while the inductanceincreases.

For this reason, for example, if surge noise is introduced into theinternal circuit 4B to cause a larger potential difference between theinternal circuit 4A and the internal circuit 4B, the potential suddenlychanges locally at and near the input element 12B and the output element13B to which the potential in the internal circuit 4A is conveyedthrough the inter-circuit signal wires 12, 13 in the internal circuit 4B(see two-dot chain lines in FIG. 12A). In such an event, conventionally,the inter-block protection circuit 4 c would mitigate the potentialdifference between the internal circuits 4A, 4B to save them fromelectrostatic breakdown while the input element 12B and so on are stillwithstanding. However, it would be difficult for the internal circuits,which suffer from a lower mitigating speed in addition to a reducedresistance to breakdown, to save themselves from electrostatic breakdown(see two-dot chain lines and so on in FIG. 12B).

Also, in such a situation, if surge noise is introduced, for example,into the input/output terminal 7B (see FIG. 12C), the existence of theinput protection circuit 3B for protecting the internal element 11B mayadversely affect the other internal element 12B and so on. The surgenoise will be forced to escape to the power lines 8B, 9B through theinput protection circuit 3BB, and then is discharged to the outside fromthe lower power terminal 5B and the ground terminal 6B, and alsopropagates and diffuses across the internal circuit 4B. In this event(see two-dot chain lines and so on in FIG. 12C), the difference betweena time required for the surge noise to reach the active element 12BP inthe first connection configuration through the power line 8B and a timerequired for the surge noise to reach the active element 12BN in thefirst connection configuration through the power line 9B cannot beignored. In addition, it is also contemplated that an element which hasbeen intensively and locally affected by the difference in potentialwith the inter-circuit signal wire 12 has also become more susceptibleto failure.

Thus, it is a technical challenge to devise a new protection circuitbased on the foregoing knowledge and precognition.

Nevertheless, since an increased integration and a larger circuit scalemake the design more and more difficult, it is also important, forintroducing a new protection circuit, to add further techniques when theprotection circuit is implemented to obviate difficulties in applyingthe automatic designing to a particular semiconductor integrated circuitdevice which may incorporate the protection circuit, and to avoiddamaging the common utilization and generalization of the semiconductorprocess.

Also, not limited to a circuit configuration in which internal circuitsusing different supply voltages are both connected to an inter-circuitsignal wire for signal transmission, interconnection of internalcircuits through certain wires may be established in otherconfigurations. For example, in addition to the provision of internalcircuits using different supply voltages, signal wires connectingexternal connection terminals through input/output circuits to theinternal circuits may be branched from the input/output circuits toroute branched wires to other internal circuits, in order to input oroutput the same external signal in some of such internal circuits.Likewise, in such a configuration, an auxiliary protection provided byprotection circuits added to input/output circuits in the middle ofwires to the internal circuits is no longer sufficient. It is thereforenecessary to provide enhanced protection for internal circuits fromelectrostatic breakdown similarly for semiconductor integrated circuitdevices having such signal wires and branched wires.

Means for Solving Problems

The present invention has been made to solve the problems set forthabove, and its object is to realize a semiconductor integrated circuitdevice which is resistant to electrostatic breakdown.

A semiconductor integrated circuit device according to a first aspect ofthe present invention invented to solve the problem mentioned above is asemiconductor integrated circuit device which has (in a single chip) aplurality of internal circuits having different power lines (for apositive voltage, a negative voltage, a higher voltage, a lower voltage,a ground, and so on), and an inter-circuit signal wire arranged tointerconnect these (at least any one pair of) internal circuits (forcommunicating signals between the internal circuits), wherein near anactive element in a first connection configuration (for inputting asignal or for outputting a signal) connected to the inter-circuit signalwire, a plurality of active elements in another connection configurationare arranged to (directly or indirectly) sandwich or surround the activeelement in the first connection configuration. The active elements inthe other connection configuration include elements of an identical orsimilar structure to the active element in the first connectionconfiguration in repetitions (of the same types or in a mixture ofdifferent types), and are connected to power lines of the internalcircuits associated therewith and isolated from signal wires other thanthe inter-circuit signal wire (specifically, any of active elements in asecond, a third, a fourth connection configuration, or protectionelements like these which are connected to power lines of the internalcircuits associated therewith but not connected to signal wires in theinternal circuit).

In the semiconductor integrated circuit according to the first aspect ofthe present invention as described above, in a normal state withoutsurge noise or the like, the newly introduced active elements in theother connection configuration are not connected to signal wires in theinternal circuit, so that the active elements in the other connectionconfiguration will not prevent proper operations of the active elementin the first connection configuration or other internal elements. On theother hand, if surge noise is introduced into an external connectionterminal and propagates through power lines, and reaches the activeelement in the first connection configuration at different times throughthe respective power lines, a portion of the surge noise is immediatelyled from the power line through which the noise had reached earlier tothe power line through which the noise has reached later through theactive elements in the other connection configuration. This operation isperformed at a plurality of locations on both sides of or around theactive element in the first connection configuration.

In this way, fluctuations in potential due to the surge noise aredispersed, though only locally, in and near the active element in thefirst connection configuration to relieve the gradient of the potentialdispersion and therefore suppress its peak to a low level. Further, thedispersion and relief are accomplished as uniformly as possible to keepthe balance at a plurality of points or multiple points in thesurroundings.

Also, as to locations for sharing the potential difference with thepotential on the inter-circuit signal wire, the potential fluctuationsare dispersed not only to a region in the active element in the firstconnection configuration connected to the power line through which thesurge has propagated earlier but also to a region connected to the powerline through which the surge has delayed, promptly added thereto, sothat the influence of the inter-circuit signal wire is also dispersed,thus further suppressing the peak of potential difference to a low levelin this respect.

Further, since the active elements in the other connection configurationnewly introduced as protection elements have the identical or similarstructure to the active element in the first connection configuration,these active elements may be implemented in a procedure similar to thatof internal elements such as the active element in the first connectionconfiguration by appropriately selecting basic cells previously arrangedin line or in matrix around the active element in the first connectionconfiguration to be protected, and connecting selected basic cells toneighboring power lines and so on, so that the newly introduced activeelements in the other connection configuration have good compatibilitywith automatic designing and maintain the common utilization andgeneralization of the semiconductor processes as before.

It is therefore possible, according to this invention, to realize asemiconductor integrated circuit device which is resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a second aspectof the present invention invented to solve the problem mentioned aboveis a semiconductor integrated circuit device which has (in a singlechip) a plurality of internal circuits having difference power lines(for a positive voltage, a negative voltage, a higher voltage, a lowervoltage, a ground, and so on), and an inter-circuit signal wire arrangedto interconnect these (at least any one pair of) internal circuits (forcommunicating signals between the internal circuits), wherein near anactive element in a first connection configuration (for inputting asignal or for outputting a signal) connected to the inter-circuit signalwire, an active element in a second connection configuration of anidentical or similar structure to the active element in the firstconnection configuration (for protection which is not connected directlyto any signal wires driven by active elements other than itself) isarranged and connected to power lines of the internal circuitsassociated therewith and isolated from the inter-circuit signal wire andother signal wires.

In the semiconductor integrated circuit according to the second aspectof the present invention as described above, the newly introduced activeelement in the second connection configuration is not connected tosignal wires in the internal circuit or to the inter-circuit signalwire, as is the case of the active element in the other connectionconfiguration, so that the active element in the second connectionconfiguration will not prevent proper operations of the active elementin the first connection configuration and so on in a normal state. Onthe other hand, if in an abnormal state in which entering surgepropagates through power lines, and reaches the active element in thefirst connection configuration at different times through the respectivepower lines, a portion of the surge noise is immediately led from thepower line through which the noise had reached earlier to the power linethrough which the noise has reached later. In this way, fluctuations inpotential due to the surge noise are dispersed near the active elementin the first connection configuration to suppress its peak to a lowlevel. Further, as to locations for sharing the influence of theinter-circuit signal wire, the influence is dispersed to locations atwhich the respective power lines are connected, thus further suppressingthe peak of potential difference to a low level.

Further, the active element in the second connection configuration newlyintroduced as a protection element is implemented in a procedure similarto that of internal elements such as the active element in the firstconnection configuration, as is the case of the aforementioned activeelements in the other connection configuration. Moreover, since theactive element in the second connection configuration can be introducedirrespective of whether a supply voltage fed to the internal circuit ishigher or lower than a supply voltage fed to another internal circuitwhich exists at an extreme end of the inter-circuit signal wire, theactive element in the second connection configuration may be readilyimplemented in a wide variety of applications.

It is therefore possible, according to this invention, to realize asemiconductor integrated circuit device which is resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a third aspect ofthe present invention invented to solve the problem mentioned above isthe semiconductor integrated circuit device according to the secondaspect of the present invention which further comprises an activeelement in a third connection configuration (for protection which is notconnected directly to any of signal wires driven by active elementsother than itself except for the inter-circuit signal wire), arrangednear the active element in the first connection configuration andincluding an element of an identical or similar structure to the activeelement in the first connection configuration, wherein the activeelement in the third connection configuration is connected to powerlines of an internal circuit associated therewith and the inter-circuitsignal wire, and isolated from other signal lines.

In the semiconductor integrated circuit device according to the thirdaspect of the present invention as described above, the active elementin the third connection configuration, though connected to theinter-circuit signal wire, is introduced only in regions where theactive element is unlikely to prevent signal transmission in a normalstate, in additional consideration to the magnitude of supply voltage.In regions where the active element in the third connectionconfiguration is likely to prevent signal transmission in a normalstate, the active element in the second connection configuration isprovided instead. Then, for surge noise as mentioned above, in additionto the aforementioned protection provided by the active element in thesecond connection configuration, the active element in the thirdconnection configuration more positively disperses the influence of theinter-circuit signal wire, though depending on the direction of thenoise, to further suppress the peak of the potential different to alower level. In addition, the active element in the third connectionconfiguration newly introduced as a protection element is alsoimplemented in a similar procedure to those of the aforementioned activeelements in the first and second connection configurations.

It is therefore possible, according to this invention to realize asemiconductor integrated circuit device which is more resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a fourth aspectof the present invention invented to solve the problem mentioned aboveis the semiconductor integrated circuit device according to the thirdaspect of the present invention, wherein a plurality of theinter-circuit signal wires having different communication directionsfrom each other are arranged in (at least) any one pair of the pluralityof internal circuits, the active element in the second connectionconfiguration and the active element in the third connectionconfiguration are arranged near the active element in the firstconnection configuration on a reception side (i.e., for inputtingsignals) of the inter-circuit signal wire in one of the pair of internalcircuits (i.e., an internal circuit which is fed with a relatively lowersupply voltage), and (preferably, a plurality of) the active elements inthe third connection configuration are arranged instead of or exclusiveof the active element in the second connection configuration (i.e,without providing the active element in the second connectionconfiguration), near the active element in the first connectionconfiguration on a reception the (i.e., for inputting signals) of theinter-circuit signal wire in the other of the pair of internal circuits(i.e., an internal circuit which is fed with a relatively higher supplyvoltage).

In the semiconductor integrated circuit device according to the fourthaspect of the present invention as described above, the active elementsin the second and third connection configurations are provided incombination as appropriate in a region which is restricted inconnectivity to an active element to both the inter-circuit signal wireand the power line due to the possibility of the voltage on theinter-circuit signal wire exceeding the voltage on the power line atthat location depending on the value of a signal on the inter-circuitsignal wire (such a region is typically a reception side of theinter-circuit signal wire in an internal circuit fed with the relativelylower supply voltage, i.e., an input element), and the active element inthe third connection configuration is provided at least one and as manyas possible in a region which is free of such restriction and isvulnerable to the influence of the inter-circuit signal wire (such aregion is typically a reception side of the inter-circuit signal wire inan internal circuit fed with the relatively higher supply voltage, i.e.,an input element).

In this way, the protection provided by the active element in the thirdconnection configuration for positively distributing the influence ofthe inter-circuit signal wire is preferentially applied to a regionwhich is vulnerable to the influence of the inter-circuit signal wire tofurther suppress the peak of the potential difference to a lower levelin that region.

It is therefore possible, according to this invention to realize asemiconductor integrated circuit device which is more resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a fifth aspect ofthe present invention invented to solve the problem mentioned above is asemiconductor integrated circuit device which comprises (in a singlechip) a plurality of internal circuits having different power lines (fora positive voltage, a negative voltage, a higher voltage, a lowervoltage, a ground, and so on), and an inter-circuit signal wire arrangedto interconnect these (at least any one pair of) internal circuits (forcommunicating signals between the internal circuits), wherein aninter-circuit auxiliary wire (preferably, running in parallel with theinter-circuit signal wire) is connected to a static area (i.e., an areawhere an electrical condition does not dynamically change in a normallyoperating state such as a location to which any signal wire is notdirectly connected) near a location at which the inter-circuit signalwire is connected.

In the semiconductor integrated circuit device according to the fifthaspect of the present invention as described above, while theinter-circuit auxiliary wire is newly introduced, this wire is connectedto a location at which an electrical condition does not dynamicallychange in a normally operating state free of surge noise or the like, sothat the inter-circuit auxiliary wire will not prevent proper operationsof the active element in the first connection configuration and otherinternal elements. On the other hand, if surge noise is introduced intoany external connection terminal and propagates only to one internalcircuit to cause an increased potential difference with the otherinternal circuit to result in a sudden change in the potential locallyat an active element in the first connection configuration in the oneinternal circuit connected to the other internal circuit through theinter-circuit signal wire, the existence of the inter-circuit auxiliarywire will give rise to a similar potential change at a point near theactive element in the first connection configuration. Subsequently, ifthe potential change propagates to the active element in the firstconnection configuration, the potential of the entire active element inthe first connection configuration will also move to some degree towardthe sudden potential at the location at which the inter-circuit signalwire is connected, so that the potential difference between a locationconnected to the inter-circuit signal wire and a location not connectedto the inter-circuit signal wire is canceled by that portion in theactive element in the first connection configuration.

Thus, local potential fluctuations produced in the active element in thefirst connection configuration due to the inter-circuit signal wire isimmediately followed by other similar local potential fluctuationsproduced in its neighborhood by the inter-circuit auxiliary wire, sothat the peak of the potential difference produced in the active elementin the first connection configuration is suppressed to a low level,whereby the active element in the first connection configuration is morelikely to avoid electrostatic breakdown.

Also, the newly introduced inter-circuit auxiliary wire, its connectionto a static region, and so on can be implemented by additional changesto an associated wiring pattern or the like, and therefore will notrequire changes in the structure of the basic cells and othersemiconductor layers.

It is therefore possible, according to this invention, to realize asemiconductor integrated circuit device which is resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a sixth aspect ofthe present invention invented to solve the problem mentioned above isthe semiconductor integrated circuit device according to the fifthaspect of the present invention, wherein the static area (several staticareas connected to the inter-circuit auxiliary wire) includes a partialregion of an active element on a transmission side of the activeelements in the first connection configuration (i.e., for outputtingsignals) connected to the inter-circuit signal wire, which partialregion is connected to a power line of the internal circuit associatedtherewith, and an active element (i.e., an active element in a fourthconnection configuration for protection which is not directly connectedto any of signal wires driven by active elements other than itself) inanother connection configuration having an identical or similarstructure to the active element in the first connection configuration ona reception side (i.e., for inputting signals), arranged near the activeelement in the first connection configuration, and isolated from signalwires other than the inter-circuit auxiliary wire (except for aconnection to the power line).

In the semiconductor integrated circuit device according to the sixthaspect of the present invention as described above, the active elementin the fourth connection configuration (the active element in the otherconnection configuration), though connected to the internal-circuitauxiliary wire, is only introduced in a region where a different powersupply is not short-circuited in a normal state, in additionalconsideration to the magnitude of supply voltage. With the provision ofthe active element in the fourth connection configuration, localpotential fluctuations produced in an active element in the firstconnection configuration located near the active element in the fourthconnection configuration are not only followed by similar potentialfluctuations due to the inter-circuit auxiliary wire but also forced topositively escape through the active element in the fourth connectionconfiguration and the inter-circuit auxiliary wire.

In this way, since the influence of the inter-circuit signal wireproduced in the reception side, which is relatively more vulnerable, isdispersed to the transmission side, which is relatively more resistant,the active element in the first connection configuration is still morelikely to avoid electrostatic breakdown.

In addition, the active element in the fourth connection configurationnewly introduced as a protection element is also implemented in asimilar procedure to those of the aforementioned active elements in thefirst to third connection configurations.

It is therefore possible, according to this invention, to realize asemiconductor integrated circuit device which is more resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a seventh aspectof the present invention invented to solve the problem mentioned aboveis the semiconductor integrated circuit device according to the sixthaspect of the present invention, wherein the inter-circuit auxiliarywire is connected to a neighboring region overlapping with or close tothe partial region on the power line connected thereto, instead of thepartial region.

In the semiconductor integrated circuit device according to the seventhaspect of the present invention as described above, the inter-circuitauxiliary wire is connected to a different location which is equivalentin function because of its closeness to the partial region. This resultsin an increased width of selection during the design of wiring, andrelieved restrictions, so that the designing becomes easier. It istherefore possible, according to this invention, to realize asemiconductor integrated circuit device which is more resistant toelectrostatic breakdown and more suitable to automatic designing and soon.

A semiconductor integrated circuit device according to an eighth aspectof the present invention invented to solve the problem mentioned aboveis the semiconductor integrated circuit device according to the sixth orseventh aspects of the present invention, wherein a plurality of theinter-circuit signal wires having different communication directionsfrom each other are arranged in (at least) any one pair of the pluralityof internal circuit, an active element in a further connectionconfiguration (i.e., the active element in the second connectionconfiguration which is not directly connected to any of signal wiresdriven by active elements other than itself) having an identical orsimilar structure to the active element in the other connectionconfiguration is arranged in addition to the active element in the otherconnection configuration (i.e., the active element in the fourthconnection configuration) near an active element in the first connectionconfiguration on a reception side (i.e., for inputting signals) of theinter-circuit signal wire in one of the pair of internal circuits (i.e.,an internal circuit fed with a relatively lower supply voltage), whereinthe active element in the further connection configuration connected toa power line of the internal circuit and isolated from the inter-circuitsignal wire, other signal wires and the inter-circuit auxiliary wire,and (preferably, a plurality of) the active elements in the otherconnection configuration (i.e., the active element in the fourthconnection configuration) are arranged instead of or exclusive of theactive element in the further connection configuration (i.e., the activeelement in the second connection configuration) (i.e., without providingthe active element in the second connection configuration), near theactive element in the first connection configuration on a reception side(i.e., for inputting signals) of the inter-circuit signal wire in theother of the pair of internal circuits (i.e., an internal circuit fedwith a relatively higher supply voltage).

In the semiconductor integrated circuit device according to the eighthaspect of the present invention, the active elements in the fourthconnection configuration (the active element in the other connectionconfiguration) and the active element in the second connectionconfiguration (the active element in the further connectionconfiguration) are provided in combination as appropriate in a regionwhich is restricted in connectivity to an active element to both theinter-circuit signal wire and the power line and is vulnerable to theinfluence of the inter-circuit signal wire (such a region is typically areception side of the inter-circuit signal wire in an internal circuitfed with the relatively lower supply voltage, i.e., an input element),and the active element in the fourth connection configuration isprovided as many as possible in a region which is free of suchrestriction and is vulnerable to the influence of the inter-circuitsignal wire (such a region is typically reception side of theinter-circuit signal wire in an internal circuit fed with the relativelyhigher supply voltage, i.e., an input element).

In this way, the protection provided by the active element in the fourthconnection configuration for positively distributing the influence ofthe inter-circuit signal wire is preferentially applied to a regionwhich is vulnerable to the influence of the inter-circuit signal wire tofurther suppress the peak of the potential difference to a lower levelin that region.

It is therefore possible, according to this invention to realize asemiconductor integrated circuit device which is still more resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a ninth s aspectof the present invention invented to solve the problem mentioned aboveis the semiconductor integrated circuit device according to the secondto eighth aspects of the present invention, wherein a plurality of theactive elements in the second, third, other, and further connectionconfigurations or those corresponding thereto (i.e., protection elementsarranged near the active element in the first connection configuration,and connected to a power line of the internal circuit associatedtherewith but not connected to signal wires in the internal circuit) arearranged to (directly or indirectly) sandwich or surround the activeelement in the first connection configuration (in repetitions of thesame type or in mixture of different types).

In the semiconductor integrated circuit device according to the ninthaspect of the present invention as described above, surge noise isbypassed or dispersed at a plurality of locations such as on both sidesor around the active element in the first connection configuration, sothat the surge noise is substantially uniformly mitigated to keep thebalance at a plurality of points or multiple points.

This enhances the protection for the active element in the firstconnection configuration more than situations where a single protectionelement is provided or the protection element is provided only on oneside of the active element in the first connection configuration.

It is therefore possible, according to this invention to realize asemiconductor integrated circuit device which is still more resistant toelectrostatic breakdown and suitable to automatic designing and so on.

A semiconductor integrated circuit device according to a tenth aspect ofthe present invention invented to solve the problem mentioned above is asemiconductor integrated circuit device, wherein, for a signal wirewhich originates from an external connection terminal, passes through aninput/output circuit in one of a plurality of sets comprised of any ofthe internal circuits and any of the input/output circuits, connected todifferent power lines, and reaches the internal circuit included in thesame set as the input/output circuit, a first protection circuit isprovided in the input/output circuit of the one set for the signal wireto protect the internal circuit of the one set from electrostaticbreakdown, and additionally, for a branched wire which is branched fromthe signal wire and reaches an internal circuit in any of the pluralityof sets, a second protection circuit is provided in the input/outputcircuit in the other set after the branched wire is passed through theinput/output circuit of the other set before it reaches the internalcircuit of the same set, and a third protection circuit is also providedin the internal circuit in the other set for the branched wire, so thatthe internal circuit in the other set can be protected fromelectrostatic breakdown at multiple stages.

A semiconductor integrated circuit device according to an eleventhaspect of the present invention invented to solve the problem mentionedabove is the semiconductor integrated circuit device according to thetenth aspect of the present invention, wherein in a region where it isdifficult to directly connect a portion or all of protection elementsincluded in the first, second and third protection circuits to thesignal wire or the branched wire due to a difference in supply voltageor the like, an active element is connected to a power line of anassociated input/output circuit or an associated internal circuit, andisolated from any signal wire such that the active element acts as aprotection element.

A semiconductor integrated circuit device according to a twelfth aspectof the present invention invented to solve the problem mentioned aboveis the semiconductor integrated circuit device according to the tenth oreleventh aspects of the present invention, wherein the third protectioncircuit includes a plurality of protection elements which are arrangedto sandwich or surround an element to be protected, thereby protectingthe element from the surroundings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a circuit diagram illustrating in detail a main portion in asemiconductor integrated circuit, device according to a first embodimentof the present invention;

FIG. 1B is a layout diagram of the main portion illustrated in FIG. 1Ain the semiconductor integrated circuit device according to the firstembodiment of the present invention;

FIG. 1C is a vertically sectioned perspective view illustrating asemiconductor region and a gate, which constitute a basic unit, in thesemiconductor integrated circuit device according to the firstembodiment of the present invention;

FIG. 2A is a circuit diagram illustrating in detail a main portion in asemiconductor integrated circuit device according to a second embodimentof the present invention;

FIG. 2B is a layout diagram of the main portion illustrated in FIG. 2Ain the semiconductor integrated circuit device according to the secondembodiment of the present invention;

FIG. 3 is a circuit diagram illustrating in detail a main portion in asemiconductor integrated circuit device according to a third embodimentof the present invention;

FIG. 4A is a circuit diagram illustrating in detail a main portion in asemiconductor integrated circuit device according to a fourth embodimentof the present invention;

FIG. 4B is a layout diagram of the main portion illustrated in FIG. 4Ain the semiconductor integrated circuit device according to the fourthembodiment of the present invention;

FIG. 5A is a circuit diagram illustrating in detail a main portion in asemiconductor integrated circuit device according to a fifth embodimentof the present invention;

FIG. 5B is a layout diagram of the main portion illustrated in FIG. 5Ain the semiconductor integrated circuit device according to the fifthembodiment of the present invention;

FIG. 6 is a circuit diagram illustrating in detail a main portion in asemiconductor integrated circuit device according to a sixth embodimentof the present invention;

FIG. 7 is a schematic diagram generally illustrating the layout on amain surface of a semiconductor integrated circuit device according to aseventh embodiment of the present invention;

FIG. 8A is a layout diagram illustrating a protection circuit and so onin an internal circuit in the semiconductor integrated circuit deviceaccording to the seventh embodiment of the present invention;

FIG. 8B is a vertically sectioned perspective view illustrating asemiconductor region and a gate, which constitute a basic unit, in thesemiconductor integrated circuit device according to the seventhembodiment of the present invention;

FIG. 9 is a circuit diagram of a protection circuit and portionsdirectly associated therewith in the semiconductor integrated circuitdevice according to the seventh embodiment of the present invention;

FIG. 10A is a schematic layout diagram of an entire chip forillustrating the technical background, showing a general layout of asemiconductor integrated circuit device having a plurality of internalcircuits using different power lines;

FIG. 10B is a circuit diagram of a main portion of the chip shown inFIG. 10A for illustrating the technical background;

FIG. 11A is a detailed circuit diagram illustrating portions of internalcircuits which communicate signals therebetween, at an element level,for illustrating the technical background;

FIG. 11B is a layout diagram of a semiconductor region for illustratingthe technical background;

FIG. 11C is a layout diagram of the semiconductor regions in which gatesand power lines have been additionally patterned for illustrating thetechnical background;

FIG. 11D is a layout diagram of the semiconductor regions in whichsignal wires have been further patterned for illustrating the technicalbackground;

FIG. 11E is a vertically sectioned perspective view illustrating asemiconductor region and a gate which constitute a basic unit forillustrating the technical background; and

FIGS. 12A–12C illustrate adverse influences of surge noise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred modes for implementing semiconductor integrated circuitdevices according to the present invention will hereinafter be describedin specific manner with reference to the following first to seventhembodiments.

A first embodiment illustrated in FIGS. 1A to 1C embodies theaforementioned first, second and ninth solutions; a second embodimentillustrated in FIGS. 2A and 2B embodies the aforementioned first, thirdand ninth solutions; and a third embodiment illustrated in FIG. 3embodies the aforementioned first, fourth and ninth solutions.

In addition, a fourth embodiment illustrated in FIGS. 4A and 4B embodiesthe aforementioned first, fifth, sixth and ninth solutions; a fifthembodiment illustrated in FIGS. 5A and 5B embodies the aforementionedfirst, fifth, seventh and ninth solutions; and a sixth embodimentillustrated in FIG. 6 embodies the aforementioned first, eighth andninth solutions.

Further, a seventh embodiment illustrated in FIGS. 7 to 9 embodies theaforementioned tenth to twelfth solutions.

It should be noted that the discussions previously given in Descriptionof Technical Background are similarly applied to the respectiveembodiments, so that repetitive description will be omitted and thefollowing discussion will be focused on differences between the priorart and the respective embodiments.

First Embodiment

A first embodiment of a semiconductor integrated circuit deviceaccording to the present invention will be described in terms of itsspecific configuration with reference to FIGS. 1A to 1C. FIG. 1A is adetailed circuit diagram of a main portion; FIG. 1B is a layout diagramof the main portion; and FIG. 1C is a vertically sectioned perspectiveview illustrating a semiconductor region and a gate which constitute abasic unit.

This semiconductor integrated circuit device comprises a plurality ofinternal circuits having different power lines, i.e., an internalcircuit 4A having power lines 8A, 9A and an internal circuit 4B havingpower lines 8B, 9B; an inter-circuit signal wire 12 extending betweenthese internal circuits 4A, 4B; an output element 12A included in theinternal circuit 4A and connected to a signal transmission side of theinter-circuit signal wire 12; and an input element 12B included in theinternal circuit 4B and connected to a signal reception side of theinter-circuit signal wire 12. While the semiconductor integrated circuitdevice of the first embodiment is identical to the aforementioned priorart semiconductor integrated circuit device 1 in that p-type MOS(hereinafter abbreviated as the “pMOS”) transistors 12AP, 12BP andn-type MOS (hereinafter abbreviated as the “nMOS”) transistors 12AN,12BN are active elements in a first connection configuration, the firstembodiment differs from the semiconductor integrated circuit device 1 inthat the following components are added near the active elements in thefirst connection configuration.

Specifically, with respect to a basic cell to which the active element12AP in the first connection configuration is allocated, a basic cell onthe left side is allocated a pMOS transistor 21, and a basic cell on theright side is likewise allocated a pMOS transistor 23. Also, withrespect to a basic cell to which the active element 12AN in the firstconnection configuration is allocated, a basic cell on the left side isallocated an nMOS transistor 22, and a basic cell on the right side islikewise allocated an nMOS transistor 24. Similarly, with respect to abasic cell to which the active element 12BP in the first connectionconfiguration is allocated, a basic cell on the left side is allocated apMOS transistor 25, and a basic cell on the right side is allocated apMOS transistor 27. With respect to a basic cell to which the activeelement 12BN in the first connection configuration is allocated, a basiccell on the left side is allocated an nMOS transistor 26, and a basiccell on the right side is likewise allocated an nMOS transistor 28.

Within the foregoing transistors, the pMOS transistors 21, 23 have theirsources and gates connected to the power line 8A, and their drainsconnected to the power line 9A. The nMOS transistors 22, 24 have theirsources and gates connected to the power line 9A, and their drainsconnected to the power line 8A. Similarly, the pMOS transistors 25, 27have their sources and gates connected to the power line 8B, and theirdrains connected to the power line 9B, while the nMOS transistors 26, 28have their sources and gates connected to the power line 9B, and theirdrains connected to the power line 8B.

A plurality of such MOS transistors 21–28 are all positioned nearassociated active elements in the first connection configuration tosandwich the active elements on both left and right sides. A pair of MOStransistors sandwiching an active element are of the same conductivetype as the active element, i.e., the p-type if the sandwiched activeelement is p-type, and the n-type if the active element is n-type. TheMOS transistors 21–28 are connected only to the power lines 8A, 9A, 8B,9B of the associated internal circuits 4A, 4B, but are not connected tothe inter-circuit signal wire 12 or other signal wires, and function asactive elements in a second connection configuration for protecting theassociated active elements in the first configuration from thesurroundings. Moreover, the allocation and/or a wiring pattern for theseMOS transistors 21–28 can be readily automatically processed by, forexample, previously adding local library cells to a design tool forautomatic wiring, and specifying an appropriate library cell to eachactive element in the first connection configuration, or by allowingappropriate library cells be automatically specified in response to thegeneration of inter-circuit signal wires.

The following discussion will be centered on the operation of thesemiconductor integrated circuit device according to the firstembodiment when in use.

While the MOS transistors 21–28 are connected to the power line pairs8A+9A, 8B+9B, each of the MOS transistors 21–28 has its source and gateconnected, so that it does not conduct and therefore never affects notonly supply voltages but also the voltage on the inter-circuit signalwire 12, the operation of the output element 12A and the operation ofthe input element 12B in a normally operating state.

It should be noted however that due to the nature of active element, therespective MOS transistors 21–28 have parasitic capacitance, though verylittle, in active regions such as pn junctions, so that instantaneousnoise or the like can be passed in both directions to some degree.Further, in the respective active elements provided in the basic cellsof this embodiment (for example, see the nMOS transistor 22 in FIG. 1C),recognition is given to the existence of a parasitic diode (22 d) whichbecomes conductive to begin operating in response to the drainattempting to swing abnormally to the negative side, and a parasitictransistor (22 t) which becomes conductive to begin operating inresponse to the drain jumping abnormally deep into the positive side.

Then, assuming that surge noise has been introduced into the internalcircuit 4B and first reached the input element 12B through the powerline 8B but has not reached through the power line 9B, the pMOStransistor 12BP has its source connected to the power line 8B and itsgate regulated by the inter-circuit signal wire 12 to a potential in theinternal circuit 4A free of noise, so that a potential differencedevelops intensively across the source and the gate of the pMOStransistor 12BP, thus causing the gate oxide film of the pMOS transistor12BP to face a crisis of electrostatic breakdown.

However, the surge noise on the power line 8B reaches the MOStransistors 25–28 immediately near the pMOS transistor 12BPsubstantially simultaneously with the arrival to the source of the pMOStransistor 12BP. Then, the surge noise is forced to escape to the powerline 9B through parasitic capacitance of these MOS transistors, and alsothrough the parasitic diode 22 d and the parasitic transistor 22 t,depending on a particular noise condition, more positively to the powerline 9B.

In this way, a surge current flowing into the source of the pMOStransistor 12BP is dispersed and slightly reduced.

Since the surge noise flowing into the power line 9B immediatelytransmits to the source of the nMOS transistor 12BN, a potentialdifference develops across the source and the gate of the nMOStransistor 12BN, whereby a charge existing near the input element 12B onthe inter-circuit signal wire 12 is bisected to the gates of thetransistors 12BP, 12BN.

In the manner described above, the gate oxide film is instantaneouslyrelieved more from the likelihood of electrostatic breakdown.

Furthermore, since the surge current flowing into the MOS transistors25–28 causes simultaneous rising and falling of the potentials at backgates and so on within regions in which the MOS transistors 25–28 arelocated (associated regions in the substrate or wells), the potentialsat the drains of the transistors 12BP, 12BN are also changed in the samedirection as those at the sources to some degree to the accompaniment ofthe varying potentials. The changes in the potentials also cause chargeson the inter-circuit signal wire 12, which have attempted to deviatetoward the sources in the transistors 12BP, 12BN, to be dispersed to thedrains.

Consequently, the surge noise promptly reaching the input element 12Bthrough the power line 8B is rapidly dispersed by the surrounding MOStransistors 25–28 to the neighborhood. Then, in the meantime, the surgenoise also reaches through the power line 9B, and the regulationperformed through the inter-circuit signal wire 12 is supplemented bythe internal circuit 4A. However, since such delayed noise has its peeklimited on the way to the input element 12B, the possibility ofdestroying the gate oxide film by electrostatic breakdown is relativelylow. Thus, the input element 12B is more reliably protected fromelectrostatic breakdown by distributing and mitigating the surge noisewhich has reached earlier.

Although repetition of detailed description is omitted, the inputelement 12B and the output element 12A are more reliably protected fromelectrostatic breakdown in a similar manner against surge noise whichpropagates first on the other power lines 9B, 8A, 9A.

Second Embodiment

Next, a second embodiment of the semiconductor integrated circuit deviceaccording to the present invention will be described in terms of itsspecific configuration with reference to FIGS. 2A and 2B. FIG. 2A is adetailed circuit diagram of a main portion, and FIG. 2B illustrates thelayout in the main portion.

The semiconductor integrated circuit device of the second embodimentdiffers from the first embodiment in that the MOS transistors 21–24 areremoved from the surroundings of the output element 12A in the internalcircuit 4A, and the nMOS transistors 26, 28 have their drains connectedto the inter-circuit signal wire 12 instead of the power line 8B in theinternal circuit 4B.

With the modified configuration set forth above, the pMOS transistors25, 27 remain as active elements in the second connection configurationfor protecting the active element 12BP in the first connectionconfiguration from both left and right sides, whereas the nMOStransistors 26, 28 are positioned near the active element 12BN in thefirst connection configuration so as to sandwich the active element 12BNon both left and right sides. While the nMOS transistors 26, 28 are ofthe same n-type as the associated active element 12BN in the firstconnection configuration and are connected to the power line 9B in theinternal circuit 4B and the inter-circuit signal wire 12, the nMOStransistors 26, 28 are not connected to other signal wires so that theyfunction as active elements in a third connection configuration forprotecting the active element 12BN in the first connection configurationfrom the surroundings.

In this case, the nMOS transistors 26, 28, though causing a slight delayin rising and falling of a signal on the inter-circuit signal wire 12,will not become conductive as long as a voltage on the inter-circuitsignal wire 12 and a voltage on the power line 9B are not inverted orexcessively separated, so that they will not damage proper operations ofthe internal circuits 4A, 4B.

Then, as surge noise reaches the input element 12B through the powerline 8B earlier than through the power line 9B, the surge noise isdispersed to the nearby power line 9B and so on and mitigated by thepMOS transistors 25, 27 in a manner similar to the foregoing. In thisevent, in addition to this operation, the active elements 26, 28 in thethird connection configuration become conductive by their diodeoperation or punch-through operation to force the surge noise to escapefrom the power line 9B to the inter-circuit signal wire 12 together withan actual current, if the potential difference between the power line 9Band the inter-circuit signal wire 12 is inverted or excessivelyseparated.

Consequently, the potential difference between the inter-circuit signalwire 12 and the power lines 9B, 8B is more positively prevented fromincreasing than in the first embodiment to suppress the peak of thepotential difference between gate and source & drain in the activeelements 12BP, 12BN in the first connection configuration, therebysufficiently reducing the likelihood of electrostatic breakdown to thegate oxide film of the input element 12B.

It should be noted that although the active elements 12AP, 12AN in thefirst connection configuration in the internal circuit 4A are alsoaffected by the surge noise flowing into the inter-circuit signal wire12, the output element 12A is less susceptible to electrostaticbreakdown by virtue of the surge noise suppressed by parasiticinductance of the inter-circuit signal wire 12 in addition to theinter-circuit signal wire 12 being connected to the drains, not to thegates, of the constituent active elements of the output element 12A inthe first connection configuration. From this point of view, the MOStransistors 21–24 are removed to make better trade-off between theefficiency of protection and an increase in the number of elements.

Third Embodiment

Next, a third embodiment of the semiconductor integrated circuit deviceaccording to the present invention will be described in terms of itsspecific configuration with reference to FIG. 3 which illustrates adetailed circuit diagram of a main portion of the semiconductorintegrated circuit device.

The semiconductor integrated circuit device of the third embodimentdiffers from the second embodiment in that the former is explicitlyprovided additionally with an inter-circuit signal wire 13 on whichsignals are sent and received in the reverse directions to theinter-circuit signal wire 12, and similar protection measures are takenlikewise for this inter-circuit signal wire 13.

Specifically, for the inter-circuit signal wire 12, no protectiveelements are added to the output element 12A on the transmission side ofthe inter-circuit signal wire 12, while active elements 25, 27 in thesecond connection configuration and active element 26, 28 in the thirdconnection configuration are mixedly provided around the input element12B on the reception side of the inter-circuit signal wire 12 asprotective elements. For the inter-circuit signal wire 13, on the otherhand, no protective elements are added to the output element 13B on thetransmission side of the inter-circuit signal wire 13, while four MOStransistors 31–34 are provided around the input element 13A on thereception side of the inter-circuit signal wire 13 as protectiveelements.

Within these protective elements, the transistors 31, 33 are pMOStransistors having the same structure as the active element 13AP in thefirst connection configuration, and are positioned on the left and rightsides of the active element 13AP in the first connection configuration.The transistors 32, 34 in turn are nMOS transistors having the samestructure as the active element 13AN in the first connectionconfiguration, and are positioned on the left and right sides of theactive element 13AN in the first connection configuration. Also, all ofthese transistors 31–34 have their sources and gates connected to thepower line 8A in the internal circuit 4A, and their drains connected tothe inter-circuit signal wire 13, but are not connected to other signalwires, so that they function as active elements in the third connectionconfiguration for protecting the active elements 13AP, 13AN in the firstconfiguration from the surroundings. In this way, the semiconductorintegrated circuit device of the third embodiment does not comprise anyactive element in the second connection configuration but merelycomprises a plurality of active elements in the third connectionconfiguration near the active element 13A in the first connectionconfiguration on the reception side of the inter-circuit signal wire 13.

With this configuration, the internal circuits 4A, 4B are protected fromelectrostatic breakdown related to the inter-circuit wire 12 in a mannersimilar to the aforementioned embodiments. Also, with respect to theinter-circuit wire 13, the nMOS transistors 32, 34 will not becomeconductive as long as the voltage on the inter-circuit signal wire 13and the voltage on the power line 9A are not inverted or excessivelyseparated, as is the case of the aforementioned nMOS transistors 26, 28.Similarly, the pMOS transistors 31, 33, though causing a slight delay inrising and falling of a signal on the inter-circuit signal wire 13 dueto the voltage on the power line 8A being normally higher than thehighest voltage on the inter-circuit signal wire 13 driven by the powerline 8B, will not become conductive as long as the voltage on theinter-circuit signal wire 13 and the voltage on the power line 9A arenot inverted or excessively separated. As a result, proper operations ofthe internal circuits 4A, 4B are also maintained in this respect.

Thus, the input element 13A is positively protected against theinter-circuit signal wire 13 by all of the four additional transistors31–34 located therearound, thereby providing stronger protection thanthe protection against the inter-circuit signal wire 12.

Consequently, the semiconductor integrated circuit device of the thirdembodiment can appropriately prevent electrostatic breakdown caused bysurge noise or the like in a situation illustrated in FIG. 12C whilemaximally limiting an increase in circuit scale.

Fourth Embodiment

Next, a fourth embodiment of the semiconductor integrated circuit deviceaccording to the present invention will be described in terms of itsspecific configuration with reference to FIGS. 4A and 4B. FIG. 4A is adetailed circuit diagram of a main portion, and FIG. 4B illustrates thelayout in the main portion.

The semiconductor integrated circuit device of the fourth embodimentdiffers from the foregoing second embodiment illustrated in FIGS. 2A, 2Bin that an inter-circuit auxiliary wire 29 is introduced.

The inter-circuit auxiliary wire 29, which is provided for eachinter-circuit signal wire 12, is routed along the inter-circuit signalwire 12 to match transmission conditions including a propagation delaytime and so on between the two wires. Therefore, the inter-circuitauxiliary wire 29 runs in parallel with the inter-circuit signal wire12.

The inter-circuit auxiliary wire 29 has one end connected directly tothe source of the pMOS transistor 12AP in the internal circuit 4A (seeFIG. 4B). This source region is a partial region connected to the powerline 8A in the internal circuit 4A in the active element 12AP on thetransmission side within the active elements in the first connectionconfiguration connected to the inter-circuit signal wire 12, and can besaid to be a static area near a connection to the inter-circuit signalwire.

With the introduction of the inter-circuit auxiliary wire 29, nMOStransistors 26, 28 have their drains connected to the inter-circuitauxiliary wire 29 instead of the inter-circuit signal wire 12.Specifically, the inter-circuit auxiliary wire 29 has the other endconnected to the transistors 26, 28 in the internal circuit 4B. Withsuch connections, the transistors 26, 28 act as active elements in afourth connection configuration having the identical or similarstructure to the active element 12BN in a first connection configurationon the reception side of signal transmission, are positioned near theactive element 12BN, and are isolated from signal wires other than theinter-circuit auxiliary wire 29. It can therefore be said that these arealso static areas.

Further, with the introduction of the inter-circuit auxiliary wire 29,the pMOS transistor 21 and the nMOS transistor 22, described in thefirst embodiment illustrated in FIGS. 1A to 1C, are again used in theinternal circuit 4A. These transistors are connected in a manner similarto the first embodiment, and act as active elements in the secondconnection configuration positioned near the input element 12B.

In this circuit configuration, any of the inter-circuit auxiliary wire29 and the nMOS transistors 26, 28 is not connected to signal wires inthe internal circuits 4A, 4B, and the nMOS transistors 26, 28 will notbecome conductive as long as the voltage on the power line 8A and thevoltage on the power line 9A are not inverted or excessively separated,so that the introduction of the inter-circuit auxiliary wire 29 will notdamage proper operations of the internal circuits 4A, 4B. In addition,since the nMOS transistors 26, 28 and so on are isolated from theinter-circuit signal wire 12, signals on the inter-circuit signal wire12 will not be delayed or reduced, the semiconductor integrated circuitdevice of the fourth embodiment provides preferred performance, andmoreover can be readily applied even to applications which require fastoperations.

For surge noise which may vary in propagation speed on the power lines8B, 9B as set forth above, the active elements 25, 27 in the secondconnection configuration act to disperse and mitigate the surge noise.In addition, the inter-circuit auxiliary wire 29 and so on act on surgedispersed near the input element 12B or surge noise which maycollectively vary the potentials in a zone including the input element12B within the internal circuit 4B, if any, in the following manner.

Specifically, an abnormally varying potential near the active element12BN in the first connection configuration will be transferred to thesource of the active element 12AP in the first connection configurationwithin the internal circuit 4A through the active elements 26, 28 in thefourth connection configuration and the inter-circuit auxiliary wire 29,and also propagates to the drain of the active element 12AP due to itsparasitic capacitance or the like. Since the drain is connected to theinter-circuit signal wire 12, the varying potential returns to the gatesof the active elements 12BN, 12BP in the first connection configuration,while it is attenuating.

In this way, a potential difference between the gate and the source ofthe input element 12B caused by the surge noise can be reduced ormitigated.

Also, the active elements 21, 22 in the second connection configurationwithin the internal circuit 4A, in addition to mitigating surge noisedirectly introduced into the internal circuit 4A in a manner similar tothe active elements 25, 27 in the second connection configuration,disperse secondary potential variations caused by the source of theactive element 12AP in the first connection configuration to aneighborhood of the output element 12A with the aid of the inter-circuitauxiliary wire 29, as described above, to directly protect the outputelement 12A as well as to indirectly protect the input element 12B.

It should be noted that while a larger number of the active elements inthe second connection configuration should be provided near the activeelement 12A in the first connection configuration in the internalcircuit 4A from a viewpoint of enhanced protection capability, they donot directly contribute to applications, so that only two of such activeelements are provided in the internal circuit 4A for the trade-off withlimitation to an increase in circuit scale.

As described above, the semiconductor integrated circuit device of thefourth embodiment can appropriately prevent electrostatic breakdowncaused by the surge noise in the situations illustrated in FIGS. 12A,12B as well as in FIG. 12C while maximally limiting an increase incircuit scale.

Fifth Embodiment

Next, a fifth embodiment of the semiconductor integrated circuit deviceaccording to the present invention will be described with reference toFIGS. 5A and 5B. FIG. 5A is a detailed circuit diagram of a mainportion, and FIG. 5B illustrates the layout in the main portion.

The semiconductor integrated circuit device of the fifth embodimentdiffers from the fourth embodiment illustrated in FIGS. 4A and 4B inthat the inter-circuit auxiliary wire 29 has its end near the outputelement 12A connected to the power line 8A instead of the source of theactive element 12AP in the first connection configuration.

Specifically, as a location for the power line 8A connected to theinter-circuit auxiliary wire 29, selection is made to an upper portionof a source region of the pMOS transistor 12AP, functioning as an activeelement in the first connection configuration (see FIG. 5B). If thislocation is not available, selection is made to any location in an upperportion of a region occupied by the pMOS transistor 12AP. If even thislocation is not available, selection is made to any location in an upperportion of the basic cell region to which the pMOS transistor 12AP isallocated. The connecting location of the inter-circuit auxiliary wire29 selected in this way lies within a neighboring region overlapping orclose to the source region (partial region) in the power line 8A.

In the fifth embodiment, the pMOS transistor 12AP also has the sourceconnected to the power line 8A, and the connection is usually made at alocation where the source region of the pMOS transistor 12AP overlapswith the power line 8A or is extremely close to the power line 8A, sothat the fifth embodiment is substantially identical to the fourthembodiment in which the inter-circuit auxiliary wire 29 is directlyconnected to the source of the active element 12AP in the firstconnection configuration in the propagation of surge noise between theinter-circuit auxiliary wire 29 and the active element 12AP in the firstconnection configuration, and so on.

Sixth Embodiment

Next, a sixth embodiment of the semiconductor integrated circuit deviceaccording to the present invention will be described in terms of itsspecific configuration with reference to FIG. 6 which illustrates acircuit diagram of a main portion.

The semiconductor integrated circuit device of the sixth embodimentdiffers from the fifth embodiment in that the former is explicitlyprovided additionally with an inter-circuit signal wire 13 on whichsignals are sent and received in the reverse directions to theinter-circuit signal wire 12, and similar protection measures are takenlikewise for this inter-circuit signal wire 13 with an inter-circuitauxiliary wire 39 and so on.

Specifically, the inter-circuit auxiliary wire 39 extends from thesource of the active element 13BP in the first connection configurationof the output element 13B on the transmission side of the inter-circuitsignal wire 13 within the internal circuit 4B to the internal circuit 4Aalong the inter-circuit signal wire 13. Also, within the internalcircuit 4B, a pMOS transistor 35 and an nMOS transistor 36, connected asactive elements in the second connection configuration identical to theaforementioned protection transistors 21, 22, are provided near theactive elements 13BP, 13BN in the first connection configuration. Withinthe internal circuit 4A, on the other hand, four MOS transistors 31–34are provided as protective elements near the active element 13A in thefirst connection configuration on the reception side of theinter-circuit signal wire 13.

Within the four MOS transistors, the transistors 31, 33 are pMOStransistors having the same structure as the associated active element13AP in the first connection configuration, and are positioned on theleft and right sides of the active element 13AP in the first connectionconfiguration. The transistors 32, 34 in turn are nMOS transistorshaving the same structure as the associated active element 13AN in thefirst connection configuration, and are positioned on the left and rightsides of the active element 13AN in the first connection configuration.Also, all of the transistors 31–34 have their sources and gatesconnected to the power line 8A in the internal circuit 4A, and theirdrains connected to the inter-circuit auxiliary wire 39, but are notconnected to other signal wires, so that they function as activeelements in the fourth connection configuration for protecting theactive elements 13AP, 13AN in the first configuration from thesurroundings. In this way, the semiconductor integrated circuit deviceof the sixth embodiment does not comprise any active element in thesecond connection configuration but merely comprises a plurality ofactive elements in the fourth connection configuration near the activeelement 13A in the first connection configuration on the reception sideof the inter-circuit signal wire 13. It should be noted that an activeelement in the second connection configuration and an active element inthe fourth connection configuration are arranged in combination near theactive element 12B in the first connection configuration on thereception side of the inter-circuit signal wire 12, as is the case ofthe aforementioned embodiment.

With this configuration, the internal circuits 4A, 4B are protected fromelectrostatic breakdown related to the inter-circuit wire 12 and theinter-circuit auxiliary wire 29 in a manner similar to theaforementioned embodiments. Also, with respect to the inter-circuitsignal wire 13 and the inter-circuit auxiliary wire 39, the nMOStransistors 32, 34 will not become conductive as long as the voltage onthe power line 8B and the voltage on the power line 9A are not invertedor excessively separated, as is the case of the aforementioned nMOStransistors 26, 28. Similarly, the pMOS transistors 31, 33 will notbecome conductive as long as the voltage on the power line 8B and thevoltage on the power line 8A are not inverted or excessively separated.For this reason, the introduction of the inter-circuit auxiliary wire 39will not damage proper operations of the internal circuits 4A, 4B. Inaddition, since the transistors 31–36 are all isolated from theinter-circuit signal wire 13, signals on the inter-circuit signal wire13 will not be delayed or reduced.

Thus, the input element 13A is positively protected against theinter-circuit signal wire 13 by all of the four additional transistors31–34 located therearound, thereby providing stronger protection thanthe protection against the inter-circuit signal wire 12.

Consequently, the semiconductor integrated circuit device of the sixthembodiment can appropriately prevent electrostatic breakdown caused bysurge noise or the like in all the situations illustrated in FIGS. 12Ato 12C while maximally limiting an increase in circuit scale.

Seventh Embodiment

Next, a seventh embodiment of the semiconductor integrated circuitdevice according to the present invention will be described in terms ofits specific configuration with reference to FIGS. 7 to 9. Thissemiconductor integrated circuit device 1 (see FIG. 7) is also formed byCMOS-based large scaled integrated circuits on a single chip in a basicstructure similar to the aforementioned embodiments. In the seventhembodiment, however, the internal-circuit signal line 12 may or may notbe provided, whereas the existence of a branched wire 45B or a branchedwire 45A has an important meaning.

Specifically, while external connection terminals 2 such as bondingpads, external signal input/output circuits and internal circuits arearranged in order from the periphery to the center of the device 1. Aninternal circuit 4A and an internal circuit 4B separately located on theleft and right sides are fed with different supply voltages, forexample, five volts and three volts, respectively, so that two separateinput/output circuits 3A, 3B are provided on the left and right sides,respectively, and a pair of power lines 8A, 9A are routed for a set ofthe input/output circuit 3A and the internal circuit 4A, while a pair ofpower lines 8B, 9B are routed for a set of the input/output circuit 3Band the internal circuit 4B.

A large number of external connection terminals 2 are likewise dividedinto the left and right sides and allocated to the respective sets,wherein the power line 8A is connected to a high power terminal SA, thepower line 9A is connected to a ground terminal 6A, the power line 8B isconnected to a low power terminal 5B, and the power line 9B is connectedto a ground terminal 6B. The remaining external connection terminals 2are assigned to appropriate external signal input/output signals, andconnected to associated signal wires which extend to the internalcircuits of the same sets through the associated input/output circuits.For example, a signal wire 44A connected to the input/output terminal 7Apasses through the input/output circuit 3A and reaches the internalelement 41A in the internal circuit 4A belonging to the same set as theinput/output circuit 3A. A signal wire 44B connected to the input/outputterminal 7B in turn passes through the input/output circuit 3B andreaches the internal element 41B in the internal circuit 4B belonging tothe same set as the input/output circuit 3B.

For the signal wire 44A, a first protection circuit 3XA is provided inthe input/output circuit 3A, and the branched wire 45B is branched fromthe first protection circuit 3XA. The branched wire 45B, after branched,extends separately from the set of the input/output circuit 3A and theinternal circuit 4A, and once passes through the input/output circuit 3Bin the other set. Eventually, the branched wire 45B reaches the internalcircuit 4B of the same set, and is connected to an input element 42B inthe internal circuit 4B. For the branched wire 45B, a second protectioncircuit 43B is provided in the input/output circuit 3B, and a thirdprotection circuit comprising components 53–56 is provided near theinput element 42B in the internal circuit 4B.

Similarly, for a signal wire 44B, a first protection circuit 3XB isprovided in the input/output circuit 3B, and a branched wire 45Abranched from the protection circuit 3XB extends separately from the setof the input/output circuit 3B and the internal circuit 4B. The branchedwire 45A passes through the input/output circuit 3A in the other set,reaches the internal circuit 4A in the same set, and is connected to aninput element 42A. For this branched wire 45A, a second protectioncircuit 43A is provided in the input/output circuit 3A, and thirdprotection circuit comprising components 63–66 is provided near theinput element 42A in the internal circuit 4A.

The first protection circuit 3XA (see FIG. 9) is composed of a diode D1having a cathode connected to the power line 8A and an anode connectedto the signal wire 44A; a diode D2 having a cathode connected to thesignal wire 44A and an anode connected to the power line 9A; and a firstprotection element 51 implemented by a pMOS transistor (active element)having a source and a gate connected to the power line 8A and a drainconnected to the power line 9A. These components are positioned close toone another. Likewise, the first protection circuit 3XB is composed ofsimilar diodes D4, D5 and first protection element 61 (active element),similarly connected to the power lines 8B, 9B and the signal wire 44B,which are positioned close to one another.

The second protection circuit 43A is composed of a diode D6 having acathode connected to the power line 8A and an anode connected to thebranched wire 45A; a diode D7 having a cathode connected to the branchedwire 45A and an anode connected to the power line 9A; and a secondprotection element 62 implemented by a pMOS transistor (active element)having a source and a gate connected to the power line 8A and a drainconnected to the power line 9A. These components are positioned in closeproximity to one another. Likewise, the second protection circuit 43B iscomposed of similar diode D3 and second protection element 52 (activeelement), similarly connected to the power lines 8B, 9B and the branchedwire 45B, which are positioned close to one another. However, no diodeis provided between the branched wire 45B and the power line 8B becausea voltage on the branched wire 45B can be higher than a voltage on thepower line 8B in a normally operating state.

Further, the input element 42A is composed of a pair of transistors42AP, 42AN having their drains connected to each other. The transistor42AP has a source connected to the power line 8A, while the transistor42AN has a source connected to the power line 9A, and their gates areconnected to the branched wire 45A. Then, the third protection circuit63–66 for the input element 42A comprises third protection elements 63,65, each of which is a pMOS transistor (active element) having a sourceand a gate connected to the power line 8A, and a drain connected to abranched wire 45A, and third protection elements 64, 66, each of whichis an nMOS transistor (active element) having a source, and a gateconnected to a power line 9A and a drain connected to the branched wire45A.

Likewise, the input element 42B is composed of a pair of similartransistors 42BP, 42BN respectively connected to the power lines 8B, 9Band the branched wire 45B in a similar manner. The third protectioncircuit 53–56 for the input element 42B comprises four third protectionelements 53, 54, 55, 56, wherein the third protection elements 54, 56implemented by nMOS transistors (active elements) have their sources andgates connected to the power line 9B and drains connected to thebranched wire 45B, as is the case of the third protection elements 64,66, while the third protection elements 53, 55 implemented by pMOStransistors (active elements) have their drains connected to the powerline 9B, neither to the branched wire 45B nor to other signal wires,unlike the third protection elements 63, 65, in order to avoidconduction in a normally operating state. The third protection elements53, 55 have their sources and gates connected to the power line 8B.

As described above, the first protection elements 51, 61 included in thefirst protection circuits 3XA, 3XB; the second protection elements 52,62 included in the second protection circuits 43A, 43B; and the pMOStransistors 53, 55 of the third protection elements included in thethird protection circuit 53–56 are all connected to the power lines ofthe input/output circuits or the internal circuits associated therewith,but are not connected to any signal wires including the branched wires45A, 45B and therefore isolated.

Also, since an element to be protected is sandwiched on both sides by aplurality of protection elements included in the third protectioncircuit, the transistor 53 is positioned on the left side of thetransistor 42BP; the transistor 55 is positioned on the right side ofthe same; the transistor 54 is positioned on the left side of thetransistor 42BN; and the transistor 56 is positioned on the right sideof the same, near the input element 42B. Similarly, near the inputelement 42A, the transistor 65 is positioned on the left side of thetransistor 42AP; the transistor 63 is positioned on the right side ofthe same; the transistor 66 is positioned on the left side of thetransistor 42AN; and the transistor 64 is positioned on the right sideof the same.

For fabricating such circuits on a silicon wafer, generally, miniaturebasic cells for active elements are repeatedly arranged at regularpitches in the vertical and horizontal directions in regions allocatedto the internal circuits 4A, 4B in each chip. In this way, the basiccells for active elements are regularly arranged in the same structureor similar structure until the midway of pre-processing of thesemiconductor process to provide highly generalized wafers. As theallocation of active elements is specifically determined based on aparticular application, a variety of demands are rapidly responded byproviding appropriate metal wiring and so on. In this event, the samebasic cells as the foregoing are frequently used (see FIG. 8A).

When a specific allocation of active elements has been determined, apair of transistors 42BP, 42BN, for example, are allocated to adjacentbasic cells in the internal circuit 4B. Subsequently, the thirdprotection elements 53, 54 are allocated to adjacent basic cells on theleft side of the respective transistors 42BP, 42BN, while the thirdprotection elements 55, 56 are allocated to adjacent basic cells on theright side of the respective transistors 42BP, 42BN, and necessary wiresassociated with these elements are substantially uniquely determined.Specifically, respective basic cells of interest are formed with contactholes (represented by black circles in FIG. 8A) such as via holes on thecenters of the cells, through which the sources of the transistors 42BP,42BN and the third protection elements 53, 54, 55, 56 are connected tothe power lines 8B, 9B, respectively. Also, for the drains and gates ofthe respective transistors, the aforementioned connections areestablished by metal wires (represented by thick lines in FIG. 8A).

In the semiconductor integrated circuit device configured as described,the MOS transistors 51, 52, 53, 55, 61, 62, though connected between thepower line pairs 8A+9A, 8B+9B, have their sources and gates connected,so that these MOS transistors will not become conductive in a normallyoperating state, thus exerting no influence on the supply voltages orthe operations of the input elements 42A, 42B. Likewise, while the MOStransistors 54, 56, 63, 64, 65, 66 have their drains connected to thebranched wires 45A, 45B, they will not become conductive in a normallyoperating state and therefore will not affect proper operations of theinput elements and so on as well as the supply voltages.

It should be noted however that due to the nature of active element,these MOS transistors have parasitic capacitance, though very little, inactive regions such as pn junctions, so that instantaneous noise or thelike can be passed in both directions to some degree. Further, also inthe protection elements provided in the basic cells of this embodiment(for example, see the nMOS transistor 55 in FIG. 8B), recognition isgiven to the existence of a parasitic diode (55 d) which becomesconductive to begin operating in response to the drain attempting toswing abnormally to the negative side, and a parasitic transistor (55 t)which becomes conductive to begin operating in response to the drainjumping abnormally deep into the positive side.

The MOS transistors will become conductive if instantaneous noise,impossible in a normally operating state, is applied, or if thesource-drain voltage is inverted or abnormally separated.

The diodes D1–D7 in turn are isolated from the power line 8B and thebranched wire 45B, so that these diodes will not affect the supplyvoltages or proper operations of the input elements and so on in thenormally operating state.

The diodes, however, become conductive if supply voltages at theirconnected locations are inverted, or if associated signal voltages andsupply voltages are inverted.

For this reason, ESD surge (surge noise) entering, for example, from theinput/output terminal 7A is first forced to escape to the power lines8A, 9A by the conductive diodes D1, D2 in the first protection circuit3XA. In this event, if the ESD surge flows more to one power line toproduce an unbalanced state, the protection element 51 also becomeconductive to disperse the ESD surge uniformly between the power lines8A, 9A. As a result the ESD surge is attenuated. Next, as the ESD surgereaches the second protection circuit 43B through the branched wire 45B,the conductive diode D3 forces the ESD surge to escape to the power line9B, and the conductive protection element 52 also disperses the ESDsurge to the power line 8B, so that the ESD surge is also attenuated onthis route.

The still survival ESD surge reaches the input element 42B furtherthrough the branched wire 45B, where the third protection elements 54,56 force the ESD surge to escape to the power line 9B, and theconductive third protection elements 53, 55 disperses the ESD surge tothe power line 8B, so that the ESD surge is further attenuated.Moreover, since the ESD surge propagates immediately to the sources ofthe transistors 42BP, 42BN from both sides, large changes in thepotential on the branched wire 45B and the gate potentials of thetransistors 42BP, 42BN cause their source potentials to promptly changein the same direction by a certain amount as if they follows thesechanges. Thus, the difference in the gate-to-source potential betweenthese transistors is further prevented from extending.

In this way, even the input element 42B, which has been difficult toprotect due to the noise incoming through the input/output circuit 3Ahaving a different power system, is reliably protected fromelectrostatic breakdown.

The input element 42A is also protected by a multi-stage structurecomprised of the first protection circuit 3XB, the second protectioncircuit 43A and the third protection circuit 63–66 from ESD surge comingthrough the input/output terminal 7B substantially in a similar manner.The input element 42A, however, is more reliably protected since theinversion of the voltages on the branched wire 45A and the power line 8Ais directly mitigated by the existence of the diode D6, the thirdprotection elements 63, 66 having the drains connected to differentlocations, and so on.

Also, even if surge noise introduced into any other external outputterminal 2, which is not connected to the branched wire 45A or 45B,causes a sudden change in the voltages on the power lines 8A, 9A, 8B, 9Bassociated with the input elements 42A, 42B to begin increasing thepotential differences across the sources and gates of the transistors42AP, 42AN, 42BP, 42BN of the input elements 42A, 42B, the thirdprotection circuits 53–56, 63–66 promptly disperse and mitigate thepotential differences at least in and around these regions.Consequently, the peak of the potential differences is suppressed.

In this way, the internal circuits are reliably protected fromelectrostatic breakdown due to surge noise entering from any externalconnection terminal 2.

Other Supplements

While the foregoing embodiments have been described in connection withthe internal circuits composed of CMOS elements, this is a mere example,and the present invention can be applied to any internal circuitscomposed of FETs of pMOS, nMOS, other NMOS, or the like. Also, theinternal circuits may contain bipolar transistors and may be digitalcircuits or analog circuits.

The number of internal circuits is not limited to two, and three or moreinternal circuits may be provided. The layout of the internal circuitsare not limited to the side-by-side arrangement, and any arbitraryarrangement may be made.

The power lines are not either limited to a pair of a positive voltageapplying line and a ground line as described above, but may be a varietyof combinations such as a pair of positive and negative voltage applyinglines, a set of a positive voltage line, a negative voltage line and aground line, a set of a higher voltage line, a lower voltage line andanother reference voltage line, and so on.

Further, for convenience of illustration, active elements in theinternal circuits are shown only in two rows and one column and in twolines and three columns. These active elements, however, are only aportion of the internal circuits. Generally, an internal circuit iscomposed of a more number of active elements arranged in a matrix ofmultiple lines and multiple columns.

As to the inter-circuit signal wires, the semiconductor integratedcircuit device may have only the inter-circuit signal wire 12, or onlythe inter-circuit signal wire 13, or a plurality of the inter-circuitsignal wires 12 or the inter-circuit signal wires 13. The number ofinter-circuit signal wires will never hinder the application of thepresent invention.

Also, while a p-type substrate has been mentioned in the foregoingembodiments, the substrate is not limited to the p-type but maybe n-typeor an insulating substrate, and is not limited to silicon but may begallium arsenide (GaAs).

While in the foregoing embodiments, the basic cell is composed of a setof two transistors, the basic cell is not limited to this particularconfiguration, but may be composed of only one transistor or more thantwo transistors.

Since the present invention is not provided on the assumption thatconventional input protection circuits and inter-block protectioncircuits are eliminated, the present invention may be applied afterthese conventional protection circuits are removed, or may be appliedtogether with such protection circuits.

CONCLUSION OF THE INVENTION

As will be apparent from the foregoing descriptions, a semiconductorintegrated circuit device according to a first aspect of the inventionof the present invention promptly and uniformly disperses fluctuationsin potentials due to surge noise near an active element in the firstconnection configuration to suppress the peak of the fluctuations, andnewly introduced protection elements are implemented in a proceduresimilar to that of the active elements in the first connectionconfiguration, and so on, thereby making it possible to realize asemiconductor integrated circuit device which is resistant toelectrostatic breakdown and suitable to automatic designing and so on.

Also, a semiconductor integrated circuit device according to a secondaspect of the invention of the present invention promptly dispersesfluctuations in potential due to surge noise near an active element inthe first connection configuration to suppress the peak of thefluctuations, and newly introduced protection elements in the secondconnection configuration are implemented in a procedure similar to thatof the active elements in the first connection configuration, and so on,and moreover act as protection elements irrespective of the magnitude ofsupply voltage, thereby making it possible to realize a semiconductorintegrated circuit device which is more resistant to electrostaticbreakdown and suitable to automatic designing and so on.

Further, a semiconductor integrated circuit device according to a thirdaspect of the invention of the present invention introduces activeelements in a third connection configuration which positively dispersethe influence of an inter-circuit signal wire and which is implementedin a procedure similar to those of the active elements in the first andsecond connection configurations, thereby making it possible to realizea semiconductor integrated circuit device which is more resistant toelectrostatic breakdown and suitable to automatic designing and so on.

Further, a semiconductor integrated circuit device according to a fourthaspect of the invention of the present invention employs many activeelements in the third connection configuration positioned on a receptionside of an internal circuit, which is more vulnerable to the influenceon an inter-circuit signal wire, for positively distributing theinfluence of the inter-circuit signal wire, thereby making it possibleto realize a semiconductor integrated circuit device which is moreresistant to electrostatic breakdown and suitable to automatic designingand so on.

Further, in a semiconductor integrated circuit device according to afifth aspect of the invention of the present invention, local potentialfluctuations caused by the inter-circuit signal wire and theinter-circuit auxiliary wire are superimposed to suppress the peak ofpotential differences generated in the active elements in the firstconnection configuration, and the new protection circuits can beintroduced by additionally changing associated wiring patterns, therebymaking it possible to realize a semiconductor integrated circuit devicewhich is resistant to electrostatic breakdown and suitable to automaticdesigning and so on.

Further, a semiconductor integrated circuit device according to a sixthaspect of the invention of the present invention disperses the influenceof the inter-circuit signal wire exerted to the reception side, which isrelatively vulnerable, toward the transmission side, which is relativelystrong, thereby making it possible to realize a semiconductor integratedcircuit device which is more resistant to electrostatic breakdown andsuitable to automatic designing and so on.

Further, a semiconductor integrated circuit device according to aseventh aspect of the invention relieves restrictions related to alocation at which the inter-circuit auxiliary wire is connected, therebymaking it possible to realize a semiconductor integrated circuit devicewhich is more resistant to electrostatic breakdown and more suitable toautomatic designing and so on.

Further, a semiconductor integrated circuit device according to aneighth aspect of the invention uses many active elements in the fourthconnection configuration around the reception side, which is vulnerableto the influence of the inter-circuit signal wire, for positivelydistributing the influence of the inter-circuit signal line, therebymaking it possible to realize a semiconductor integrated circuit devicewhich is more resistant to electrostatic breakdown and suitable toautomatic designing and so on.

Further, a semiconductor integrated circuit device according to a ninthaspect of the invention promptly and uniformly disperses potentialfluctuations due to surge noise near active elements in the firstconnection configuration to limit the peak of the fluctuations, so thatenhanced protection can be provided for the active elements in the firstconnection configuration, thereby making it possible to realize asemiconductor integrated circuit device which is resistant toelectrostatic breakdown and suitable to automatic designing and so on.

Further, a semiconductor integrated circuit device according to a tenthaspect of the invention protects internal circuits, to which branchedwires are routed, in the internal circuits themselves as well as ininput/output circuits in the midway, to multiply explicit and directprotection in addition to supplementary protection in input/outputcircuits in another power system, thereby making it possible to enhancethe protection of the internal circuits from electrostatic breakdown.

Further, a semiconductor integrated circuit device according to aneleventh aspect of the invention can protect internal circuits evenwithout direct connections to signal wires or branched wires, to ensurethat a protection circuit can be provided even for an internal circuitconnected to a circuit in another power system through a signal wire ora branched wire.

Further, a semiconductor integrated circuit device according to atwelfth aspect of the invention protects an element of interest from thesurroundings, so that local fluctuations in potential difference aroundthe element of interest, if any, will be dispersed to the surroundingsto promptly limit the peak of the potential difference, thereby makingit possible to further enhance the protection of internal circuits fromelectrostatic breakdown.

1. A semiconductor integrated circuit device comprising: at least twointernal circuits arranged internally in a circuit forming region, eachof said two internal circuits having a different pair of power lines; aplurality of external signal input/output circuits having inputprotection circuits connected to input/output terminals outside said twointernal circuits; an inter-circuit signal wire, different from saidpower lines, arranged to interconnect said two internal circuits,wherein said inter-circuit signal wire is not directly connected to saidexternal signal input/output circuits; and an inter-circuit auxiliarywire, different from said power lines, connected to a static area near alocation at which said inter-circuit signal wire is connected.
 2. Asemiconductor integrated circuit device according to claim 1, whereineach of said internal circuits includes a multiplicity of basic cellsfor active elements regularly arranged in repetition.
 3. A semiconductorintegrated circuit device according to claim 1, further comprising asubstrate formed in a single chip, and said circuit forming region isallocated to one surface of said substrate.
 4. A semiconductorintegrated circuit device according to claim 3, wherein said circuitforming region includes signal input/output circuits outside saidinternal circuits, and external connection terminals outside saidinput/output circuits.
 5. A semiconductor integrated circuit deviceaccording to claim 1, further comprising: a first transistor on areception side, connected to said inter-circuit signal wire, in one ofsaid two internal circuits; and a plurality of second transistors, forprotecting said first transistor, being arranged adjacent to said firsttransistor in said one of said two internal circuits and including atransistor of an identical structure to said first transistor, whereinsaid inter-circuit auxiliary wire is connected to one of a pair of powerlines on a transmission side in the other of said two internal circuitsand said plurality of second transistors in said one of said twointernal circuits.
 6. A semiconductor integrated circuit deviceaccording to claim 5, wherein said plurality of second transistors arearranged to sandwich or surround said first transistor.
 7. Asemiconductor integrated circuit device according to claim 5, whereineach of said internal circuits includes a multiplicity of basic cellsregularly arranged in repetition, and said first transistor and saidplurality of second transistors are allocated to some of said basiccells.
 8. A semiconductor integrated circuit device according to claim5, further comprising a substrate formed in a single chip, and saidcircuit forming region is allocated to one surface of said substrate. 9.A semiconductor integrated circuit device according to claim 8, whereinsaid circuit forming region includes signal input/output circuitsoutside said internal circuits, and external connection terminalsoutside said input/output circuits.
 10. A semiconductor integratedcircuit device according to claim 5, wherein said first transistor is ann-type MOS transistor and said transistor of an identical structure tosaid first transistor is an n-type MOS transistor.
 11. A semiconductorintegrated circuit device according to claim 10, wherein a drain of saidtransistor of an identical structure to said first transistor isconnected to said inter-circuit auxiliary wire.